1. Field of the Invention
The present invention relates to a cooling unit used for instance in an automotive air conditioner, more particularly, relates to an air conditioner with a refrigerant evaporator placed in a duct, which comprises a refrigerant-refrigerant heat exchange portion for performing heat exchange between refrigerant passing through an inlet passage and refrigerant passing through an outlet passage.
2. Description of the Related Art
In a refrigerant evaporator as a component of a cooling unit for an air conditioner, it is desirable to keep the amount of refrigerant distributed to plural refrigerant evaporation passages even in order to improve the heat exchanging efficiency (cooling efficiency).
Therefore, for example, Japanese Patent Application Laid-Open No. 5-196321 discloses a refrigerant evaporator comprising a refrigerant-refrigerant heat exchange portion having an inlet passage in which refrigerant from an expansion valve flows and an outlet passage to flow out refrigerant to a refrigerant compressor, and a refrigerant-air heat exchange portion including plural refrigerant evaporation passages passing to the inlet passage via a pressure reducing unit and evaporating the refrigerant by heat exchanging air with the refrigerant from the inlet passage.
Here, considering air flow resistance of the refrigerant-air heat exchange portion for the refrigerant evaporator, it is conceived to place the refrigerant-air heat exchange portion for the refrigerant evaporator inside a duct and to place the refrigerant-refrigerant heat exchange portion outside the duct.
In such a case, however, when the air outside the duct touches the refrigerant-refrigerant heat exchange portion, vapor in the air outside the duct condenses, which causes the drops of water adhering to the surface of the refrigerant-refrigerant heat exchange portion, because low pressured refrigerant passes within the refrigerant-refrigerant heat exchange portion. Consequently, a drain mechanism to drain the drops of water adhering to the surface of the refrigerant-air heat exchange portion in the duct needs an additional drain mechanism to drain the drops of water adhering to the refrigerant-refrigerant heat exchange portion extending outside the duct. Thus the cost of the cooling unit increases, which results in a problem to raise a price for an air conditioner.
For the purpose of solving the above mentioned problem, it is considered to employ a cooling unit including both the refrigerant-air and the refrigerant-refrigerant heat exchange portions therein and to provide a drain mechanism for the drops of water below a unit case of the cooling unit.
Regarding this cooling unit, however, since the refrigerant-refrigerant heat exchange portion is placed in the air flow passage in the unit case, the air flowing in the air flow passage from the upstream side of the refrigerant evaporator collides against the refrigerant-refrigerant heat exchange portion, which generates turbulent air flow. Thus, wind speed distribution is formed in the air passing around the plural refrigerant evaporation passages of the refrigerant-air heat exchange portion for the refrigerant evaporator, and it causes a problem in that the temperature distribution of the air passing around the plural refrigerant evaporation passages is deteriorated, even if the refrigerant is evenly distributed to the plural refrigerant evaporation passages of the refrigerant-air heat exchange portion.